STPG370 vs STKM13A
These two grades are listed as equivalents of each other: their chemistry windows overlap and they serve the same applications. They are not always identical — check the differences below before substituting, especially in certified designs.
STPG370
Pipe & Tube Steel
STPG370 is the JIS G3454 carbon steel pipe for pressure service at the 370 MPa tensile level — the Japanese counterpart class to ASTM A106 Grade A. It is a fully chemistry-controlled pipe grade (unlike the SS structural grades) for pressure piping up to about 350 °C.
Standards: DIN P235TR1 type (near) · AISI A106 Gr.A type (near) · JIS STPG370 (JIS G3454) · GB 20 (near)
STKM13A
Pipe & Tube Steel
STKM13A is a JIS G3444 carbon steel tube for machine structural purposes — the 370 MPa class tube Japanese machinery makers use for frames, rollers and mechanical parts. Its chemistry window mirrors STPG370 but the standard, tolerances and flattening/flaring tests are written for mechanical tube, not pressure pipe.
Standards: DIN E235 tube type (near) · AISI 1020 tube type (near) · JIS STKM13A (JIS G3444) · GB 20 tube (near)
Chemical composition compared (%)
| Element | STPG370 | STKM13A |
|---|---|---|
| C | ≤0.25 | ≤0.25 |
| Si | ≤0.35 | ≤0.35 |
| Mn | 0.30–0.90 | 0.30–0.90 |
| P | ≤0.040 | ≤0.040 |
| S | ≤0.040 | ≤0.040 |
Properties compared
| Property | STPG370 | STKM13A |
|---|---|---|
| Tensile strength | ≥370 MPa | ≥370 MPa |
| Yield strength | ≥215 MPa | ≥215 MPa |
| Density | 7.85 g/cm³ | 7.85 g/cm³ |
| Product form | Carbon steel pipe for pressure service (JIS G3454) | Carbon steel tube for machine structural use (JIS G3444) |
Sourcing either grade?
Nasteel stocks both families from Shenzhen with EN 10204 3.1 mill certificates by heat number.
Ask for a quotationSee full data sheets: STPG370 · STKM13A. Substitution decisions for certified parts stay with the design authority.